Lorentz and $CPT$ tests with spin-polarized solids

Abstract

Experiments using macroscopic samples of spin-polarized matter offer exceptional sensitivity to Lorentz and $CPT$ violation in the electron sector. Data from existing experiments with a spin-polarized torsion pendulum provide sensitivity in this sector rivaling that of all other existing experiments and could reveal spontaneous violation of Lorentz symmetry at the Planck scale.